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Owon 14-bit USB scopes
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2N3055:

--- Quote from: agusugid on February 08, 2023, 05:43:27 am ---
--- Quote from: jasonRF on February 07, 2023, 12:37:21 pm ---
--- Quote from: agusugid on February 07, 2023, 03:02:24 am ---
Math function is available. You can do - + * / with both channels
FFT also availale, but I think Owon should not give the function as it so useless

--- End quote ---
That is an improvement.  The subtraction function is of course key for a lot of measurements, and also a place where the extra bits can really help.

I just looked through the manual on the owon site, and they haven't updated it yet to include the math.  Does it let you pick the size of the FFT?  Or does it work like on the vds3102, where you only get a 2k FFT so just 1k frequency points?  I usually find that I want a pretty long FFT to really get the information I am looking for, but even a 2k FFT can be useful.   

jason

--- End quote ---

Attached the panel control for FFT. So Useless. Can not even show 1 khz from the channel 1 wave.

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You have to make it sample at lover sample rate if you want it to show anything at all. This is common mistake. You have only 10 periods on the screen. Set timebase to something like 10ms/div, not 500us/div and see if something starts to show up. In general FFT won't show good results (even on good implementation) if you can see details of signal in time domain..
Play with timebase a bit.
But yeah FFT is not very good.
agusugid:
Just realize that the software can not auto detect the peak freq and put it in the center of the window  |O. No autoscale at all in vertical or horizontal axis. |O
Have to manually slide the fft to find the peak freq.

As you said, the more samples, the better  :-+

8bits vs 14bits shows different fft result

Best Regards
Agus
jasonRF:
FFT looks usable - and seems like it must be larger than 2k.     :-+

I see you are in peak detect mode.  I have only used FFTs in normal sampling mode on my scopes.  Given how oversampled you still are it might not matter too much, but does the FFT look much different in normal vs peak detect?  I would especially be curious whether it changed the levels if the 2nd and 3rd harmonics. 

Jason
agusugid:

--- Quote from: jasonRF on February 08, 2023, 02:07:51 pm ---FFT looks usable - and seems like it must be larger than 2k.     :-+

I see you are in peak detect mode.  I have only used FFTs in normal sampling mode on my scopes.  Given how oversampled you still are it might not matter too much, but does the FFT look much different in normal vs peak detect?  I would especially be curious whether it changed the levels if the 2nd and 3rd harmonics. 

Jason

--- End quote ---

Image attached. I think the difference is minimal.

Agus
agusugid:
Thermal imaging for VDS6102A after 30 minutes
Room temperature about 30C
ADC and FPGA are the hottest spot
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